Re: Real Mode Improvement on Intel Hosts - GSoC Project

[Avi Kivity <avi@qumranet.com>]

Guillaume Thouvenin wrote:
> On Thu, 24 Apr 2008 11:05:39 -0500
> Anthony Liguori <anthony@codemonkey.ws> wrote:
>
>   
>> The first stage is to detect vmentry failures and run x86_emulate() for 
>> a single instruction.  If you look at the mailing list, you'll see 
>> patches from myself and Guillaume.  This should be enough to allow most 
>> Ubuntu installer CDs to work under KVM.
>>     
>
> Howdy, 
>
>   Here is the last patch I have. It can detects a vmentry failure and it
> emulates one instruction. I added the emulation of several instructions
> like "ljmp", "mov Sreg, reg", "mov reg, Sreg"... The problem I'm
> working on is that once I entered in emulation of real mode I do not
> manage to recover a VMX friendly state (in my case cs.rpl ==
> ss.rpl). So I emulate more and more instructions. 
>
>   I added a trace to see instructions that are emulated (emulation of
> 0xa8 is in progress so it currently fails):
>
> [60108.040894] emulation at (46e53) rip 6e13: ea 18 6e 18
>   

Here cs.rpl == cpl == 0

> [60108.072108] emulation at (46e58) rip 6e18: 66 b8 20 00
> [60108.103997] emulation at (46e5c) rip 6e1c: 8e d8 8c d0
> [60108.148114] emulation at (46e5e) rip 6e1e: 8c d0 81 e4
> [60108.180117] emulation at (46e60) rip 6e20: 81 e4 ff ff
> [60108.212008] emulation at (46e66) rip 6e26: c1 e0 04 01
> [60108.244926] emulation at (46e69) rip 6e29: 01 c4 66 b8
> [60108.272948] emulation at (46e6b) rip 6e2b: 66 b8 08 00
>   

mov $8, %eax

> [60108.304953] emulation at (46e6f) rip 6e2f: 8e d0 8e c0
>   
mov %eax, %ss

Here, ss.rpl == 0

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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